| 摘要 |
The device includes an operating head movable by a control unit with respect to a board for machining; the operating head includes a board holder device and an electric motor for a tool spindle; the rotor of the motor rotates with respect to the stator on air-cushion supports, and the stator slides axially on a further air-cushion support and is insulated with respect to the operating head; a signal generator senses the capacitance between the rotor and the stator, and generates an electric signal upon the tool on the spindle contacting the upper surface of the board; and the signal is used to define a reference dimension relative to the upper surface, and to so condition the control unit as to feed the tool to a predetermined depth as of the upper surface.
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